The invention relates to high strength phenolic composites made by pultrusion process.
The term xe2x80x9cpultrusionxe2x80x9d means a method of drawing a plurality of fibrous reinforcement coated with a binder solution through a heated die in order to shape the fibrous reinforcement and binder into a unitary article of desired shape.
Fibrous reinforcement, such as glass fibers, allows the formation of varying shapes by the pultrusion process. This process provides a composite structural member, which is typically stronger and lighter and may be less expensive than similarly sized single material members, such as wood. Such fiber-reinforced structures can be used as a substitute product to conventional wood or metal structural materials.
A schematic for a pultrusion process is shown in U.S. Pat. No. 5,456,781 . A plurality of fiber rovings is pulled through a resin bath and then a forming die and subsequently through a heated die that cures the resin materials and shapes the rovings and resin. Although glass fiber has been mentioned as the fiber filaments or rovings, other materials, including synthetic fibers, carbon fibers, natural fibers and inorganic fibers, e.g. ceramic, can be used in the form of filaments, rovings or mats. Suitable for use as synthetic fibers in tension are aramid fibers, which are commercially available from E.I. Dupont de Nemours and Company of Delaware under the trademark xe2x80x9cKEVLARxe2x80x9d and high modulus polyethylene, which is available under the trademark xe2x80x9cSPECTRAxe2x80x9d from Allied Fibers of Allied Signal, Petersburg, Va.
Phenolic resin systems containing resorcinol, such as a commercially available phenolic resin system containing about 0-60% resorcinol, suitable for the protrusion process are commercially available under the trade designation GP4221 from Georgia-Pacific Resins Inc.
Other phenolic resin systems for pultrusion composites are described in U.S. Pat. Nos. 5,075,413; 5,075,414; and 159,405. This patent discloses a reaction product of a resorcinol component such as a resorcinol formaldehyde novolac resin formed as the reaction product of resorcinol, an aldehyde and an acidic catalyst. The resorcinol component is reacted with a phenolic resole resin such as phenol-formaldehyde. The resulting compositions are suitable for pultrusion processes and exhibit fire resistance.
The invention is directed to a high strength pultrusion resin composition comprising a phenolic resin and an elastomeric component. In particular the present invention is directed to a pultrusion resin composition comprising about 75 wt % to about 85 wt % of a phenolic resin, about 9 wt % to about 20 wt % of the reaction product of a polyhydroxy compound and an epoxy functional polysiloxane, about 6 wt % to about 15 wt %, of a phenolic epoxy, and about 0.2 wt % to about 1 wt % of a catalyst, based on total weight of the composition.
The invention is further directed to a pultruded product prepared with the high strength pultrusion resin composition and a plurality of fibrous reinforcement.
The invention is also directed to a method of preparing a pultruded product comprising drawing a plurality of fibrous reinforcement through a bath of the high strength resin composition bath wherein the elastomeric component is added to the phenolic resin prior to or during the pultrusion process.